Coaxial cables are typically connected to interface ports, or corresponding connectors, for the operation of various electronic devices, such as cellular communications towers. Many coaxial cables are installed on cell towers which expose the coaxial cables to harsh weather environments including wind, rain, ice, temperature extremes, vibration, etc.
A typical coaxial cable/connector includes inner and outer conductors each having several interconnected, internal components. Over time, due to certain harsh environmental conditions, these internal components can lose mechanical and/or electrical contact with the interconnected components resulting in a decrease/loss of performance. For example, loose internal parts can cause undesirable levels of passive intermodulation (PIM) which, in turn, can impair the performance of electronic devices. PIM can occur when signals, at two or more frequencies, mix in a non-linear manner to produce spurious signals. The spurious signals can interfere with, or otherwise disrupt, the proper operation of the electronic devices. Unacceptably high levels of PIM in terminal sections of the coaxial cable can disrupt communication between sensitive receiver and transmitter equipment on the tower and lower-powered cellular devices. Disrupted communication can result in dropped calls or severely limited data rates.
An example of such component integration relates to the prepared end of a coaxial cable where the tip end of a center conductor engages a female RF cable connector. More specifically, the center conductor typically comprises an aluminum core having a copper outer cladding. This combination of materials is used to minimize costs by manufacturing the core (constituting 99% of the center conductor), from a low cost aluminum, and the outer cladding (constituting a small fraction of the total conductor weight), from a highly conductive, but significantly more expensive copper material. To augment the electrical contact at the tip, an electrically compatible end cap or contact can be attached to the outermost tip end of the center conductor. The female RF cable connector which engages the end cap may be fabricated from the same material as that used in the manufacture of the copper outer cladding, or other electrically compatible material such as brass.
While the addition of a highly conductive end cap can improve performance, difficulties can be encountered when attaching the end cap to the copper clad aluminum center conductor. That is, the outer cladding, which is relatively thin to minimize cost, is easily removed when connecting a tip end contact to the terminal end of the conductor. As such, it can be difficult to prepare the tip end of the center conductor without removing all or most of the thin conductive cladding. Accordingly, it can be difficult to produce a robust mechanical connection while maintaining a highly conductive electrical path from the center conductor to the tip end contact, i.e., without effecting a weld between the components due to current induced heat or micro-arcing therebetween.
Additionally, dimensional changes within the connector can adversely impact the impedance and, consequently, the passive intermodulation (PIM) produced within the coaxial cable. That is, an increase in diameter can alter the impedance of the connector which must, in turn, be compensated by the structure of the connector, i.e., the outer dimensions of the connector. Since the cable dimensions are essentially fixed, few options are available to the designer to main the impedance along the length of the connector. Accordingly, to maintain low levels of PIM, the designer can do little more than introduce new materials having different material properties when such materials become available.
Therefore, there is a need to overcome, or otherwise lessen the effects of, the disadvantages and shortcomings described above.